We have a iPad cart here at the Doucette Library that is loaded with education apps for elementary and secondary students. Although I used some apps with students in my elementary school job, it is only since I have been at the Doucette that I am learning what a great app does. When testing out apps to be loaded for teachers in training, I found that the one use, reward based, apps were the least attractive over the long term. In experimenting with apps, I found the creative apps like Book Creator or TinkerBoxHD allow students to create content on their iPad with very little training. This creativity and presentation of content is key to a good app. TinkerBoxHD allows students to learn simple physics principles though puzzle solving, then leads them to invent using these principles.
Book Creator allows students to load various kinds of content, created by their own hand or downloaded, into e-book form. How exciting for students to be writing, illustrating, and creating their own books. In loading a classroom iPad, play with each app to plan how students can use them creatively within the classroom. Oh, and one other thing I learned, listen to your students. Sometimes they know about apps you can only imagine but would be wonderful additions to your creative bag of tricks.